The working of lithium batteries is based on the conversion to electrical energy of the chemical energy generated in forming lithium compounds from lithium atoms. The reactions for the formation of the lithium compounds may be reversed by feeding electrical energy to a lithium battery, in other words, most lithium batteries may be readily recharged. In conventional non-aqueous lithium batteries, the anodic reaction comprises lithium, often intercalated in fine particles of carbon, being ionized to form a mobile lithium ion accompanied by the generation of an electron. In the recharging step of the anode or the negative electrode, lithium atom is reformed by consuming an electron. The cathodic reaction of a lithium battery entails the formation of a lithium compound by reacting a lithium ion with another reagent and simultaneously consuming an electron. Conveniently, the other reagent is a metal oxide capable of forming an oxidic compound with lithium, such as for example a vanadium oxide homologue, manganese dioxide, cobalt oxide and such like. In the recharging step of the cathode, lithium ion is released from the oxidic compound formed in the discharging reaction, simultaneously generating an electron.
Thin film non-aqueous lithium batteries are made up by layers of organic polymer laminates, and each laminate carries substances taking part in the anodic and cathodic reactions, respectively. Thus the carbon particles having elemental lithium intercalated therein are carried by a laminate of an organic polymer, thereby forming an anodic or negative electrode laminate. The metal oxides which react with the lithium ions in the cathodic reaction are carried by another laminate of organic polymer, thereby forming a cathodic or positive electrode laminate. The negative and the positive electrode laminates are separated by another polymeric laminate which carries the non-aqueous electrolyte therein. The peripheries of the negative and positive electrode laminates are often also separated by a separator laminate which separate the electrode compartments without interfering with the reactions between the negative electrode and the electrolyte, and the positive electrode and the electrolyte during the operation of the battery. The laminates contained by the thin film battery are usually sealed by known methods and are also provided with metallic current collector sheets or foils for incorporation of the battery in an electrical circuit and for electrical contact during the charging and discharging of the battery.
Thin film lithium batteries render efficient service and prolonged useful life provided full contact is rigorously maintained between the respective laminates within the battery. If the contact area between the faces of the laminates in the battery is reduced during operation the energy output of the thin film lithium battery may be seriously impaired.
Another important requirement for efficient operation of a thin film non-aqueous lithium battery is that the anodic and cathodic reactions are separated, that is, no internal short circuiting takes place by means of electron flow between the anodic and the cathodic laminates located in the battery.
Yet another important feature of a well functioning non-aqueous lithium battery is efficient sealing, since any moisture entering the battery will react with the lithium present.
A method of spring-loading to maintain contact between the reactive compartments of a fuel cell battery is described in U.S. Pat. No. 5,328,779 issued on Jul. 12 1994, to Tannenberger et al. U.S. Pat. No. 5,314,507 issued on May 24 1994, to Rossol, teaches the use of high temperature-bonding adhesive seals between a ceramic frame and the metallic terminals within the cell. However, U.S. Pat. No. 5,314,507 does not address the problem of maintaining contact between reactive surfaces of the electrode and electrolyte laminates of a thin film non-aqueous lithium battery.
There is a need for a method to maintain contact between the interactive surfaces of the polymer laminates of a thin film non-aqueous lithium battery thereby enhancing prolonged and efficient battery life, and in another respect, there is a need for a method for more effectively separating the periphery of the polymer laminates which carry the electrodes of a thin film lithium battery, while maintaining the high mobility of the lithium ions traversing the non-aqueous electrolyte.